Method of making bellows



Jan. 8, 1929. 1,698,210

F. K. BEZZENBERGER METHOD OF MAKING BELLOWS Original Filed June 25, 19242 Sheds-Sheet l FRI Q q Fig.3

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Fred KBegenberger Haw AITTOR Jan. 8, 1929. 1,698,210

F. K. BEZZENBERGER METHOD OF MAKING BELLOWS Original Filed June 25, 19242 Sheets-Sheet 2 v :INVENTOR. Fred KBenenberger Patented Jam-8,- 1929 Ip "UNITED STATES PATENT. carries.

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Application flled June 25, 1924, Serial No. (22,357. .Benewed my 28,1928.

' The present invention relates to a new and im roved method of makingexpanslble and col apsible hollow metallic walls, that is, me-

to'the maintaining ofcertain relationships between the internal andexternal pressures which I have found highly desirable in accuratelycontrolling the form of the corrugations. Tothe accomplishment oftheforegoing and related ends, said invention, then, consists of themeanshereinafter fully de scribed and particularly pointed out; in theclaims.

The annexed drawings and the following description set forth in detailone approved method of carrying out the invention, such disclosed mode,however, constituting but one of the various ways in which the principleof the invention may be used.

In said annexed drawin s:-

Fig. 1 is'a central vertica section throu h a tube mounted in positionto be corrugate between axially movable forming dies or rings;

Fig. 2 show'sa section of the same tube on a somewhat enlarged scaleafter the initial bulge has been formed in the tube wall; Fig. 1

3 is a side elevation partially in section of a tube after formationinto a bellows; Fig. 4 is a view on an enlarged scale showing a portionof the tube wall in contact with two adjacent forming rings before theformation ofany bulge in the wall; Fi 5 is a similar view showing thissection 0 a tube wall after the initial bulge; Fig. 6 is a View of asection of the tube wall after its complete formation between twoadjacent rings; Fig. 7 is a view of a 1 single corrugation on anenlarged scale; Fig. 8 is a view inperspective of a portion of the tubewall in its initial'condition; Fig. 9 is a similar view of thesame'portion of wall after the format-ion'of the initial bulge; Figs. 10and 11 are similar views showing the same portion of a tube wall in anintermediate and 4.5 in a final condition after the formation into acomplete, corrugation; Fig. 12 is a p-lan view showing the tube in itsoriginal size and (in are descri setting up an internal pressure withinatube whichjis sealed at its two ends,"except for a conduit throughwhichthe internal fluid pres-- sure is allowed to'flow, while simultaneouslyapplying a pressure against the ends'of the tube to collapse the tubeduring formation of the corrugation. In these attempts, which ed inseveral issued United States patents,'spaced forming rings or dies aredisposed about the tube in its original condition and the metal of thetube wall is then expandedloutwardly into folds between these rin s asthe tube is collapsed longitudinally,

an means are provided in these cases for allowingthe rings to collapsewith'the tube. I have tried all of the methods described in thesevarious patents and find that the ma- .chines there disclosed are inoerative to promercial metallic bellows in a single contin'uous hydraulicoperation to establish certain,

conditions and relations. These conditions and relations are asfollows 1. The spaced forming rings or dies should I be given a ratiobetween their initial point-topoint setting (by which I mean the initialdistance between the points of contact of two adjacent rings with thetube wall) and the ity and resiliency to the finished bellows to finalpoint-to-point setting of the same two render it comparable to thebellows which are today in use as manufactured by other processes. Thisrelationship (and those of the next two paragraphs) is further explainedand illustrated in myPatent No. 1,506,966 grantedSept. 2, 1924. I

2. The tube when first laced within the spaced forming rings shoul itialbulge, which is produced by setting up an internal pressure in the tubewhich is sutficient to grip the edges of the forming rings and fix eachring at a given point along the tube wall. The depth of this initialbulge will depend upon the original oint-to-point spacing between therings and the contour .Of the rings at their points of contact with thetube, a ring having a sharp edge requiring a relatively shallower bulgethan one having a rounded edge; and a narrow original point-to-pointsetting requiring a shallower bulge than a longer setting. Inexperimenting with various types of rin s and various initial spacing ofthese rings T have found that this initial bulge which is to be producedin the tube wall should not increase the tube diameter more than 40 percent of the point-to-point initial spacing, but must be deformed solneamount which varies with the original spacing of the rings and with thecontour of the rings, as set forth above. Unless this initial bulge isproduced in the tube the tube tends to slide up within the ringssomewhat during the collapsing of the tube axially, and the resultingobject is not then a bellows, but atube having a portion of uniformdiameter, and an irregular series of irregular corrugations or folds,which ordinarily occur between the fixed end of the tube and the nearestforming ring.

3. It is further desirable that the surface length of the tube measuredalong an ele- -mental longitudinal line be not increased during theformation of the corrugations and the collapsing of the tube. Thiselemental surface length should be either maintained constant duringthis operation or should be actually decreased, and it is highlydesirable in producing bellows of the types and sizes now in mostgeneral .use to actually decrease this elemental surface length duringthe formation of the bellows from the tube. The ex lanation of thisrelationship is that the tu e wall when formed into corrugations issubjected to two deforming actions, the first of which is that the tubewall is bent upon itself or doubled and collapsed at the same time,which is the only deforming action to which the tube wall would besubjected if it were a flat plate. This action requires little if anystretching of the metal and may be considered as chiefly a bending oration. The second deforming action to wiich the tube wall is subjectedis the stretching circumferentially to allow for the increase indiameter of the outer portion of each corrugation or .fold. If theelemental surface length of the tube wall is allowed'to increase duringthe formation, that means that the section of metal between any twoadjacent forming rings is being stretched during both the bend'ng andthe circumferential stretching operations, and the resultwil-l bethatthe outer portion of each corrugationwill have been worked to such adegree that itwillbe hard and brittle and the resulting vbellows willbreak during its forming. In order to prevent the metal from beingworked beond the desired extent, as would be the. case if the surfacelength were allowed to increase, I actually decrease the surface lengthofthe bellows during the forming operation, the excess metal, which waspresent in the tube wall over that required if the tube wall were a fiatsheet and were merel bent into the form of a fold, being allowe to flowcircum ferentially to compensate for the increased diameter of thebellows at the outer portion of the fold, with the result that Iamenabled to maintain the temper of the metal in the outer fold at from10 to 20 per cent, which renders the bellows fairly soft and capable ofa great number of fiexures before breakage.

4. A fourth condition which is highly de sirable in order to accuratelycontrol the form of corrugations is a certain relationship between theinternal pressure produced in the tube and the longitudinal pressureexerted against the ends of the tube to collapse it during the formingaction. As I have already stated it is desirable to initially set up aslight bulge in the tube wall to fix the rings at the proper pointsagainst the wall. The pressure which is necessary to produce this bulgealso acts against the ends of the tube, and if, as in the present case,one end of the tube is open and is sealed by a plug while the other endis closed by an end wall of the tube, it is there necessary at thebeginning to exert only enough pressure against this closed end of thetube to counterbalance the downward pressure of the fluid pressure inthe tube.

This downward pressure is a product ofthe pressure per square inch inthe tube times the effective area of the end wall, and an external forceshould be exerted axially against the end of the tube substantiallyequal to this internal axial force.

As the tube wall is forced upwardly to roduce corrugations and as thetube is colapsed axially to assist in this formation some metal isforced to flow circumferentially in each corrugation to compensate forthe increased diameter as the corrugation goes up. This operation is nota bending operatlon, but is an actual flowing of the metal and requires.considerable force to accomplish. Accordingly, the axial pressure on theend of the tube should be progressively increased during the formationof the bellows, and at the finish. of the operation should be materiallyhigher than the internal pressure exerted against the efiective area ofthe end wall of the bellows.

The penalty for not maintaining this relationship is the bucklinginwardly of the tube wall if the axial pressure is too high inproportion to the internal pressure, and failure to form and collapsethe'tube at all if the axial pressure is too low compared to theinternal pressure;

5. In order to make a bellows quickly and p to accurately and quicklyreturn the forming rings to their initial spaced position for repeatingthe operation it ishighly desirable to positively and mechanicallycollapse and return the rings in time with the axial movement of theplunger or ram, which involves the interconnection of the ram with themeans 7 for moving the rings. This desirable condition is met in themachine described in'my patent heretofore identified.

Referring now to the drawings, in Fig. 1 there isshown a tube 1 which isopen at the upper end 2 and which has this end sealed betweenfrustro-conical members 3 and 4,

the member 4 being provided with an opening 5, through which fluidpressureis forced into the tube. This tube is disposed between a seriesof spaced formin rings 7 8, 9,10, 11,

16 and the lowermost ring 7, the plunger in this case acting as both anaxially movable ram to collapse the-tube and as one of the formingrings.

The desirability for the relationship between the initial oint-to-pointset-ting'of the rin and the al point-to-point setting, an also thedesirability for the synchronizing of the movement of the'axiallymovable ram and the rings has already been fully explained in my patentabove referred to. I will therefore now take up the various otherconditions, the desirability for which has already been explained.

When the tube is first disposed within the rings thereis no grippingengagement be.- tween the rings and the tube wall, and the tube wall ifcollapsed axially by means of the ram would slide at least betweencertain of the rings and produce a very irregular object, which wouldcertainly not be a bellows having uniform corrugations. Therefore, afterthe tube is disposed within the rings I induce a pressure in the tubewhich is sufficient' to bulge the metal outwardly between the rings, asshown in Fig. 2, the bulge being sufiicient to cause a positlveengagement between each ring and a properly corresponding portion of thetube wall, which engagement ismaintained during the remainder of theoperation, and until the bellows is removed from the apparatus. Duringthis initial expanding of the tube wall the metal is actually stretchedand is not bent, sincethe rings'are maintained at their original spacingand the metal is stretched both radially and slightly circumferentiallyduring the action of throwing out this initial bulge. This con- .ditionis shown in Figs. 4 and 5, in which a section 20 of the tube wall isshown between rings ,7 and 8 and these rings are maintained in the samerelationship'during this expan;

=-sortion of the originaltube wall is subjected uring the forminoperation we find that such portion 25 of t e wall-(see Fig. 8) is firstforced outwardly into the shape shown in Fig. 9, in which the-ed e of 'alongitudinally cut section is increas in lengthalthough maintainedbetween dies-7 and 8, which are.

is, the distances A and A in igs. 8 and 9 are the same, but the lengthF,which is the length of the section of-the original tube maintained attheir original s aeing. That measured along an elemental line, is lessthan the len h F, which isthe dimension of the same e go of the. section25. after thefirst bulging operation! Similarly, the dimension C, whichis the width measured circumferentially of the segment 25 of theoriginal tube is less than the dimension C, which is the width of thesame section after the first bulging operation. As this section is stillfurther formed into the corrugation, as shown in Figs. 10 and 11, thedistance A successively becomesA in Fig.- 10 and A in Fig. 11, thisdistance representing the s acing between the rings as they arecollapsed: While the dimension F actually decreases, and in Fig. 10 isslightly'smaller than in Fig. 9, and is still smaller in Fig. 11 asindicated at F and F.

The metal which would thus have to be compacted to thicken up the'wallof the corrugation if a flat sheet were being bent is now forced'eireumferent-ially to compensatefor the increased diameter whichisrepres'ented by the increasing dimensions C in Fig. 10 and C in Fig.11, and which is shown still better in Figs. 12 and 13.

The initial width of the section 25 is shown at B in Fig. 12, and at thefinish of the corrugating operation thisportion of the tube wall hasbeen expanded circumferentially until its width is C (see Figs. 12 and13), and the excess metal which was initially disposed in the tube. wallbetween the two adjacent rings is I flowed circumferentially to providefor this increase in diameter of each corrugation.

The increase in diameter is thus produced pressureexerted by the endwall.

In order to illustrate the relationship bei tween the internal fluidpressure and the external axial pressure acting on the tube it may bestated that in the formation of a bellows from a tube of soft brasswhere the tube has an initial diameter of 1% inches and is expanded intoabellows having an outside diameter of 2 inches, I initially set up apressure of 390 pounds per square inch'inside of the tube. In this samecase the initial spacing between the rings is .750 of an inch, the finalsurface len h of one corrugation is .696 of an inch, an the thickness ofthe tube wall initially is .0065 of an inch. In corrugating this tubethe pressure is maintained constant within the tube at 390 pounds andthe external axial pressure is initially sufiicient to counterbalancethe internal pressure exerted against the end of the tube, it beingunderstood that a tube having either two open ends or a single open endmay be corrugated. At the finish of the corrugating operation theexternal axial pressure-has been increased by 373 pounds, that is, thereis an absolute pressure exerted against the end' of the tube of 37 3pounds, which is the collapsing pressure employed to collapse thecorrugations, shorten the surface length of each corrugation and forcethe metal into complete contact with the collapsed rings in the mannerdescribed.

Other modes of applying the principle of my invention may be employedinstead of the one explained, change being made as regards theprocessherein disclosed, provided the step or steps stated by any of thefollowing claims or the equivalent of such stated step or steps beemployed. a

I therefore particularly point out and distinctly claim as my invention2- 1. In a method of making a metallic bellows from a tube completely byfluid pressure, the steps which consist in mounting a tubeconcentrically within a series of spaced axial- 1y movable formingrings, initially establishing a fluid pressure within said tubesufficient to expand the tube wall slightly between said rings and thenpositively collapsing said rings and-simultaneously, progressively andmaterially increasing the axial external pressure from a pressurebalancing the axial internal pressure to a pressure materially above thesame to collapse the tube into corrugations lying between said rings.

. 2. In a method-of making a metallic bellows from a tube completely byfluid pressure, the steps which consist in mounting a tubeconcentrically within a series of spaced axially movable forming rings,initially establishing a fluid pressure within said tube sufiicient toexpand the tube wall slightly between said rings while maintaining saidrings stationary and exerting an axial pressure against each end of saidtube substantially equal to the product of the internal fluid pressuretimes the area, and then positively collapsing said rings a'ndsimultaneously, progressively and materially increasing the pressureexertedagainst the ends of said tube to collapse the same intocorrugations lying between said rings.

3. In a method of making a metallic bellows from a tube completely byfluid pressure, the steps which consist in mounting a tubeconcentrically within a series of spaced axially movable forming ringsand between a fixed support at one end and a movable ram at the otherend, establishing an initial fluid pressure within said tube andexpanding the wall radially, e. g. a distance less than 20 per cent ofthe distance between said rings, while maintaining said rings stationaryand exerting a. pressure by said ram against one end of said tube equalto the internal fluid pressure acting axially on said end, and thenprogressively and positively collapsing said rings axially whileprogressively increasing the pressure of said ram sufliciently tooverbalance the internal pressure exerted on said tube end and to flowthe metal of the tube wall in the forming corrugations circumferentiallyto compensate for the increasing diameter of such corrugations and toshorten the longitudinal surface length of said tube wall.

4. In a method of making a metallic bellows from a tube by fluidpressure, the steps which consist in mounting a tube concentricallywithin a series of spaced axially movable forming rings, bulging saidtube between said rings by exerting fluid pressure interiorly thereofwithout exerting pressure axially of the tube to collapse the same, andthen forming the corrugations by the combined action of internal fluidpressure and a progressively increasingcollapsing pressure actingaxially of the tube.

5. In a method of making a metallic bellows from a tube by fluidpressure, the steps which consist in mounting a tube concentricallywithin a series of spaced axially movable forming rings, bulging thetube between said rings by internal fluid pressure while balancing saidpressure in an axial direction, and then forming the corrugations by thecombined action of internal fluid pressure and a progressively increasincollapsing pressure acting on the tube axizilly of the 1 balancing theactionof said pressure axially of the tube, and then exerting aprogressively increasing axial pressure on the tube greater than thepressure therein to form the corrugations by the combined action of thecollapsing pressure on the tube and the internal fluld pressure actingradially of the same.

7. Ina method of making a metallic bellows from a tube by fluidpressure, the steps which consist in mounting a tube concentricallywithin aseries of spaced axially movable forming rings, subjecting saidtube interiorly to fluid pressure, and then while maintaining aninternal fluid pressure exertwhile gradually increasing said axialpressure.

9. The method of making flexible corru- I gated tubular Walls whichincludes positionmg a tube in operative relation to a die, subjectingsaid tube to fluid pressure, applying a pressure to said tube in thedirection of its axis to aid said fluid pressure in collapsning saidtube into said die, and increasing said axialpressure asthe tube isbeing col- 20 lapsed into said die.

Signed by me this 24th 'day of June, 1924.

FRED K. BEZZENBERGER;

